1. Field of the Invention
The present invention relates to an apparatus and process for determining the deformability of red corpuscles in the blood.
The red corpuscle which has a diameter of about 7.5 microns, has the form of a disk whose section is that of a biconcave lens. This form, particularly adapted to gas exchanges, contributes to the elasticity and deformability of the red corpuscle, which are required for its tubulent journey through blood flow ducts and more particularly in capillaries some of which scarcely exceed 2 to 3 microns in diameter, i.e. appreciably less than that of the red corpuscle. The deformability of the red corpuscle is a property which is more and more investigated, not only for fundamental research but for clinical research. Thus, too great a red blood corpuscle rigidity leads to hematological (anemias) and microcirculatory irregularities which in extreme cases may lead to the death of the subject (drepanocytoses). The measurement of the deformability of the red corpuscles is therefore a scientific and clinical necessity.
2. Description of the Prior Art
Nurmerous methods have been proposed and developed i.e. the rigidity of the red corpuscle. These methods may be classed in two categories:
First category called comprehensive methods: the measurement is carried out on the whole of the corpuscle. To this category belong: PA1 Second category, called individual methods: each measurement is made on an individual and the results are averaged. To this category belong: PA1 a measurement cell formed from two electrically insulated parts, or compartments (for example made from a plastic material), clamped mechanically one against the other, each of these parts comprising input and output orifices as well as a cavity having a lateral hole, one of the cavities containing a buffer, the other being intended to receive the suspension to be measured; PA1 a vertical filter holder clamped between the two parts of the measurement cell at the very position of the two lateral holes; PA1 a vertically mounted filter formed by a commercially available membrane made from a plastic material, of a thickness of the order of 3 to 20 microns having pores whose diameter is between 3 and 5 microns, said membrane being obstructed by a mask over the major part thereof so as to leave only a small and limited number of pores, of the order of 15 to 100 pores, open to the flow; PA1 two electrodes, one in each of said cavities placed at the height of the filter holder opposite the filter; PA1 an electronic device for translating the electric impedance variation into the transit time of the corpuscles. PA1 a suspension of red blood corpuscles is prepared by diluting a small volume of red corpuscles in a large volume of isotonic conducting buffer, so as to obtain a volume concentration of the order of 0.01 to 1%; PA1 the two cavities of the measurement cell are filled respectively with pure buffer and the suspension obtained by means of two needles; PA1 the flow of the suspension is established through the membrane by applying a desired over pressure in the compartment containing the suspension, the electrodes and the recording apparatus being switched on, and, PA1 the histogram of the transit times corresponding to the measured suspension is plotted.
filtration methods which are based on the flow of a suspension of red blood corpuscles through calibrated holes of a diameter less than that of the red corpuscles (see more particularly the work of Teitel P. "Blood Cells. 3, 55-70 1977"), of Hanns M. F., French Pat. No. 2 463 927 Biorheology, 20(2)199-212 1983 and still others); PA2 optical diffraction methods which are based on the analysis of the optical diffraction spot of the red corpuscles deformed by a shearing flow (see more particularly Bessis et Al. "Blood Cells" 1. 307-313 1975"); PA2 the method using the measurement of the deformability by aspiration into a micropipette: the static (aspiration) and dynamic (ejection) deformation of the corpuscle are observed; PA2 the method using the measurement of the transit time through a single pore (see more especially the work of Kiesewetter et al. "Scand. J. Clin. Lab. Invest." 41, Suppl. 156, 229-231 1981" and "Biorheology 19, 737-753 1982").
Each category, each method has its advantages and disadvantages. The comprehensive methods are much simpler but their principle defect is that they cannot reveal a subpopulation and can only give a qualitative idea. The individual methods on the other hand are much more reliable since they give a more exact image and allow the exact percentage to be detected, in other words they allow the number of rigid corpuscles to be quantified. However the individual methods are economically very expensive, and are difficult and long to carry out: For example Kiesewetter et al. (above mentioned references) use a membrane containing a single hole of the passage of the corpuscle. The times taken by the filtration experiment are extremely long, there is frequent clogging and the membranes are expensive.
The purpose of the present invention is then to provide an apparatus and a method for measuring the deformability of red corpuscles, which answer better the requirements of practice and the methods and devices known heretofore, more especially in that they are both easy to use and combine the comprehensiveness of the first category with the accuracy and reliability of the second category.